Farmers looking to reduce herbicide costs, control weeds in organic systems, or control herbicide-resistant broadleaves may find a new solution in an old technology
Rotary hoes aren’t seen much in Western Canada these days. The implement was once commonly used by soybean and corn farmers in the midwestern United States to control weeds and break up crusted soil.
For the last seven or eight years, researchers with the University of Saskatchewan and Agriculture and Agri-Food Canada have been using rotary hoes to control broadleaf weeds. Eric Johnson, a weed biologist based at the Scott Research Farm, has been testing the implement on pea and lentil crops. He’s found that pulse crops can tolerate multiple passes with the rotary hoe at any crop stage. Rotary hoes have also been used successfully in cereal crops.
Dalhousie University recommends using the rotary hoe before the crop emerges and at a later date. Farmers shouldn’t use a rotary hoe in cereals between crop emergence and at least the two-leaf stage. The rotary hoe works well in corn up to the four-leaf stage. When farmers are making a second pass, Dalhousie University suggests travelling in the opposite direction of the first pass.
Steve Shirtliffe, a University of Saskatchewan professor, says that a second pass with the rotary hoe is often needed to control broadleaves.
“The key thing with rotary hoeing is timing. You have to be out there when the weeds are just emerging. This may only be a couple of days,” Shirtliffe says.
The rotary hoe works best on weeds that are still in the white thread stage, as the roots aren’t able to anchor the weeds against the tines. Iowa State University suggests digging through trash to scout for newly emerged weeds. If the weeds are beyond the cotyledon stage, they are likely too far along for the rotary hoe to work well.
Because the weeding window is so small, a rotary hoe needs to cover many acres quickly. The rotary hoe is designed for speed, between eight to 25 kilometres per hour. Going fast doesn’t hurt weed control — in fact, going too slow renders it less effective. Field scale models of up to 60 feet are available.
Shirtliffe says the rotary hoe also works best when soil conditions are dry, but not too hard. Hot and dry post-treatment conditions are also best.
Farmers who practice no-till may be concerned about residue plugging the tines. But min till rotary hoes have two separate tines that prevent plugging. Crop residue remains on the soil surface after multiple passes.
Shirtliffe has created a video demonstrating the rotary hoe. To see one in action, visit youtube.com and search “rotary hoe weed control.” †
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